“I'm proud to support Tammy Duckworth for the seat I once held in the United States Senate,” President Obama said.

Duckworth is challenging Republican U.S. Sen. Mark Kirk. It's expected to be one of the most competitive races as Democrats try to retake control of the Senate.

Vice President Joe Biden also threw his support behind the Iraq War veteran.

Obama's comments come as Kirk has repeatedly attacked Duckworth. He says she failed to protect veterans after then-Gov. Rod Blagojevich appointed her to lead Illinois' Department of Veterans Affairs.

Both Duckworth and Kirk are veterans. Duckworth lost both legs when her Army helicopter was shot down in Iraq. Kirk is a former Navy intelligence officer.

“I'm deeply honored to receive the endorsements of President Obama and Vice President Biden. I am profoundly grateful that President Obama recognized my commitment to serve my fellow veterans and gave me the opportunity to do so in the earliest days of his administration," Duckworth said in a statement.